Corrugated cowl for combustor of a gas turbine engine and method for configuring same

ABSTRACT

A cowl for use with a combustor of a gas turbine engine, the cowl includes a main body with an annular corrugation. A combustor of a gas turbine engine, the combustor includes: a hollow body defining a combustion chamber, the hollow body having a liner; an outer cowl having an annular corrugation, the cowl connecting to the liner; and an inner cowl connecting to the liner. A method of configuring a cowl for a gas turbine engine combustor, the method includes forming an annular corrugation in a main body of the cowl.

BACKGROUND OF THE INVENTION

[0001] In a gas turbine engine, pressurized air is provided from thecompressor stage to the combustor, whereupon it is mixed with fuel andis burned in the combustion chamber. The amount of pressurized air thatenters the fuel/air mixers, and correspondingly the inner and outerpassages of the combustor, has typically been regulated by inner andouter cowls located upstream of the fuel/air mixers and the combustordome. Such cowls have been generally held in place by means of a boltedjoint that includes the combustor dome, the cowl, and either the inneror outer combustor liner. Accordingly, both the outer and inner cowls ofa gas turbine engine experience a slight change in pressure thereacross,as well as a vibratory load induced by the engine. While theseenvironmental factors have a greater effect on the outer cowl, theynevertheless cause wear on both cowls and consequently limit the lifethereof.

[0002] In addressing this problem, the prior art has generally taken oneof the following approaches. The first of which involves use of a sheetmetal body for the cowls with a lip formed at the leading edge thereof,preferably by curling or wrapping the sheet metal around a damper wire.However, it has been found that this design is life-limited due to arubbing-type wear occurring at the interface of the wire and the sheetmetal body caused by a thermal mismatch between the wire and the wrap.More specifically, the thermal mismatch causes the sheet metal to unwraparound the wire, creating a gap between the wire and the cowl. Inaddition, white noise exiting the diffuser and/or combustor acousticscreates high cycle fatigue vibratory loading of the wire against thesheet metal wrap. Thus, the combined rubbing and vibratory inducedshaking of the wire against the metal wrap result in the wrapped portionof the cowl thinning, cracking and eventually liberating sheet metal andwire fragments.

[0003] Another cowl design involves a machined ring that forms theleading edge lip of the cowl, where the ring is welded to a formed sheetmetal body. Such a machined ring provides a solid lip for the cowl,which is desirable, but circumferential welding thereof to the formedsheet metal body has resulted in stress concentrations both in andaround the weld.

[0004] A one-piece cowl design is disclosed in a U.S. patent applicationentitled “One-Piece Combustor Cowl,” U.S. Pat. No. 5,924,288, whichdiscloses a cowl that is casted with a solid lip of increased thicknessat a leading edge thereof. While suitable for its intended purpose, thiscowl tends to be both heavier and more costly than a sheet metal cowl.

SUMMARY OF THE INVENTION

[0005] The above discussed and other drawbacks and deficiencies areovercome or alleviated by a corrugated cowl. In an exemplary embodimentof the invention, a cowl for use with a combustor of a gas turbineengine, the cowl includes a main body with an annular corrugation. Inanother exemplary embodiment a combustor of a gas turbine engine, thecombustor includes: a hollow body defining a combustion chamber, thehollow body having a liner; an outer cowl having an annular corrugation,the cowl connecting to the liner; and an inner cowl connecting to theliner. A method of configuring a cowl for a gas turbine enginecombustor, the method includes forming an annular corrugation in a mainbody of the cowl.

DESCRIPTION OF THE DRAWING

[0006] Referring to the exemplary drawings wherein like elements arenumbered alike in the several Figures:

[0007]FIG. 1 is a longitudinal cross-sectional view of a gas turbineengine combustor including an outer cowl with annular corrugations andan inner cowl;

[0008]FIG. 2 is a forward looking aft view of the cowl depicted in FIG.1;

[0009]FIG. 3 is a longitudinal cross-sectional view of a gas turbineengine combustor including an outer cowl with annular corrugations andan inner cowl with annular corrugations;

[0010]FIG. 4 is a forward looking aft isometric view of both acorrugated outer cowl and a corrugated inner cowl;

[0011]FIG. 5 is an aft looking forward isometric view of the corrugatedouter and inner cowls of FIG. 3;

[0012]FIG. 6 is an enlarged, partial cross-sectional view of thecorrugated cowl depicted in FIG. 1;

[0013]FIG. 7 is an enlarged, partial cross-sectional view of thecorrugated cowl depicted in FIG. 1 illustrated with a full wrap; and

[0014]FIG. 8 is an alternative embodiment of an enlarged, partialcross-sectional view of the corrugated outer cowl depicted in FIG. 1illustrated with a partial wrap.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Referring now to FIG. 1, a single annular combustor 10 suitablefor use in a gas turbine engine is illustrated. Combustor 10 includes ahollow body 11 that defines a combustion chamber 12 therein. Hollow body11 is generally annular in form and includes an outer liner 14, an innerliner 16, and a domed end or dome 18. In the present annularconfiguration, domed end 18 of hollow body 11 further includes aplurality of air/fuel mixers 20 of known design spaced circumferentiallytherearound.

[0016] In combustor 10, an outer cowl 22 is provided upstream ofcombustion chamber 12 and attached to outer liner 14, as well as dome18, at outer bolted connection 24. An inner cowl 26 is also providedupstream of combustion chamber 12 and attached to inner liner 16, aswell as dome 18, at inner bolted connection 28. Outer and inner cowls 22and 26 perform the function of properly directing and regulating theflow of pressurized air from a diffuser of the gas turbine engine todome 18 and outer and inner passages 30 and 32 located adjacent outerand inner liners 14 and 16, respectively. It will be understood fromFIGS. 1 and 2 that outer and inner cowls 22 and 26 are annular in shapelike combustor 10. As is typical with combustor cowls, outer and innercowls 22 and 26 are axially elongated relative to a central cowl axis34.

[0017] It is desired that outer and inner cowls 22 and 26 be bothlightweight and inexpensive. In order to achieve this, outer and innercowls 22 and 26 preferably are made of sheet metal. The sheet metalmaterial for outer and inner cowls 22 and 26 may include cobalt basedalloys and nickel based alloys. In particular, the preferred AerospaceMaterial Specifications for such cobalt based alloys include AMS5608 andthe preferred Aerospace Material Specifications for such nickel basedalloys include AMS5536, AMS5878, and AMS5599.

[0018] In order to increase the stiffness of outer cowl 22, outer cowl22 is molded to form annular corrugations 40. By increasing thestiffness to outer cowl 22, the frequency of outer cowl 22 is alsoincreased. There is a proportional correlation of increased stiffness toincreased frequency; thus, as stiffness increases, so does thefrequency. It is desirable to increase the frequency of outer cowl 22 toa point in which the frequency of outer cowl 22 is higher than thefrequency of the engine.

[0019] Referring to FIG. 3, in an alternative embodiment, both outer andinner cowls 22 and 26 are formed with annular corrugations 40. FIGS. 4and 5 illustrate isometric views of outer and inner cowls 22 and 26 withannular corrugations 40.

[0020]FIG. 6 illustrates the various parameters to forming annularcorrugations in outer cowl 22. When molding annular corrugations 40,there are three parameters to annular corrugations 40: (a) the number ofannular corrugations in outer cowl 22, which is shown as “w”; (b) theheight of each annular corrugation 40, which is shown as “h”; and (c)the spacing of each annular corrugation 40, which is shown as “s”. Thetwo important parameters for forming annular corrugations 40 are thespacing, s, and the height, h, of annular corrugations 40. The spacingand height of annular corrugations are optimized so that the naturalfrequency of outer cowl 22 is increased to outside the engine operatingrange. The number of corrugations in outer cowl 22 does notsignificantly affect the stiffness of outer cowl 22.

[0021] In an exemplary embodiment, the spacing of annular corrugationsis from about 0.010 inches to about 0.500 inches, with a preferredspacing of about 0.080 inches. The height of annular corrugations isfrom about 0.010 inches to about 0.050 inches, with a preferred heightof about 0.0334 inches. By forming annular corrugations with the spacingand height in the above-indicated range, the stiffness of outer cowl 22is increased so that the frequency of outer cowl 22 is increased tooutside a typical engine operating range.

[0022]FIGS. 7 and 8 illustrate outer cowl 22 with annular corrugationswith outer cowl 22 being formed with a full wrap 50 (FIG. 7) or apartial wrap (FIG. 8). Both full wrap 50 and partial wrap 60 are locatedat a first end 62 of outer cowl 22. First end 62 is the end in which theair enters the combustor 10 (see FIG. 1). By providing for full wrap 50or partial wrap 60 at first end 62, there is a smooth surface as the airenters the combustor, which provides for improved aerodynamics. Whileeither type of wrap may be utilized with outer cowl 22, partial wrap 60is preferred because there is less forming of the body of outer cowl 22to form partial wrap 60.

[0023] Outer cowl 22 with annular corrugations 40 sustains the stresslevels imposed thereon for a desirable number of hours withoutsuccumbing to high cycle fatigue and directs air flow to the combustorin a manner consistent with the requirements of the fuel/air mixers andthe inner/outer passages. Outer cowl 22 with annular corrugations 40 isboth lightweight and inexpensive in terms of materials, processing andspecific fuel consumption. Moreover, by incorporating annularcorrugations 40 into outer cowl 22, the damper wire (not shown) of priorart cowls can be eliminated. Also, inner cowl 26 may also have annularcorrugations 40, which would have the same effect on inner cowl 26.Desired air flow into combustor 10 is typically difficult to achieve,and may be affected by any change in design for outer cowl 22. Thebenefit of including corrugations into outer cowl 22 is that there islittle to no impact on desired air flow into combustor 10, including thepassage pressure recoveries.

[0024] While this invention has been described with reference to apreferred embodiment, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A cowl for use with a combustor of a gas turbine engine, wherein theimprovement comprises an annular corrugation formed in said cowl.
 2. Thecowl of claim 1, wherein said main body is made of sheet metal.
 3. Thecowl of claim 1, wherein the cowl is an outer cowl.
 4. The cowl of claim1, wherein the cowl is an inner cowl.
 5. The cowl of claim 1, whereinsaid annular corrugation includes at least two annular corrugations. 6.The cowl of claim 5, wherein said annular corrugations has a spacingbetween each annular corrugation.
 7. The cowl of claim 6, wherein saidspacing is about 0.010 inches to about 0.500 inches.
 8. The cowl ofclaim 6, wherein said spacing is about 0.080 inches.
 9. The cowl ofclaim 1, wherein said annular corrugation has a height.
 10. The cowl ofclaim 9, wherein said height is from about 0.010 inches to about 0.050inches.
 11. The cowl of claim 9, wherein said height is about 0.0334inches.
 12. The cowl of claim 1, further comprising a partial wrapdisposed at a first end of said cowl.
 13. The cowl of claim 1, furthercomprising a full wrap disposed at a first end of said cowl.
 14. Acombustor of a gas turbine engine, the combustor comprising: a hollowbody defining a combustion chamber, said hollow body having a liner; anouter cowl having an annular corrugation, said outer cowl connecting tosaid liner; and an inner cowl connecting to said liner.
 15. Thecombustor of claim 14, wherein said inner corrugations has an innerannular corrugation.
 16. The combustor of claim 14, wherein said mainbody is made of sheet metal.
 17. The combustor of claim 14, wherein saidannular corrugation includes at least two annular corrugations.
 18. Thecombustor of claim 17, wherein said annular corrugations has a spacingbetween each annular corrugation.
 19. The combustor of claim 18, whereinsaid spacing is about 0.01 inches to about 0.50 inches.
 20. Thecombustor of claim 18, wherein said spacing is about 0.080 inches. 21.The combustor of claim 14, wherein said annular corrugation has aheight.
 22. The combustor of claim 21, wherein said height is from about0.010 inches to about 0.050 inches.
 23. The combustor of claim 21,wherein said height is about 0.0334 inches.
 24. The combustor of claim14, further comprising a partial wrap disposed at a first end of saidouter cowl.
 25. The combustor of claim 14, further comprising a fullwrap disposed at a first end of said outer cowl.
 26. The combustor ofclaim 14, further comprising a mixer disposed between said outer cowland said inner cowl.
 27. A method of configuring a cowl for a gasturbine engine combustor, the method comprising forming an annularcorrugation in a main body of the cowl.
 28. The method of claim 27,further comprising forming a second annular corrugation.
 29. The methodof claim 27, further comprising spacing said annular corrugations fromabout 0.01 inches to about 0.5 inches apart.
 30. The method of claim 27,further comprising spacing said annular corrugations about 0.08 inchesapart.
 31. The method of claim 27, further comprising forming saidannular corrugation with a height of between 0.01 inches to about 0.05inches.
 32. The method of claim 27, further comprising forming saidannular corrugation with a height of about 0.0334 inches.
 33. The methodof claim 27, further comprising forming a partial wrap at a first end ofsaid main body.
 34. The method of claim 27, further comprising forming afull wrap at a first end of said main body.